CIRC0LATIOW. 101 



A careful examination of the capillary circulation in the 

 living animal, disclosea certain irregularities in the motion 

 of the currents, which it is impossible to attribute to any 

 other than local influences, or the alternate attraction and 

 repulsion of the fluid by the tissues. Sometimes the cur- 

 rent is rapid, then slow, occasionally it stops, or its direc- 

 tion may be even reversed. 



In certain diseased states of the body, there is an unusual 

 amount of blood in the capillaries of the affected part, as 

 is evident from the amount of local inflammation ; yet the 

 general current of the circulation is not at all affected. 

 This movement of the blood into the capillaries is entirely in- 

 dependent of the heart's action, the energy of which is not 

 increased ; it therefore depends entirely on the attraction 

 exercised on it by the cells of the diseased parts. 



Any increase of energy in the vital processes of any 

 part of the organism, shows the action of local influences 

 in diverting the current of the circulation into new chan- 

 nels. Thus, the development of the uterus, during preg- 

 nancy, induces at first an unusual degree of activity in the 

 oapUlary circulation of those parts ; the necessary result of 

 the changes continually taking place in the forming tissues. 

 An increased supply of blood is attracted in the direction 

 of the developing organs of the ibetus, and there is a 

 gradual enlargement of the diameter of the arterial trunk 

 through which it is transmitted. In the meanwhile, the 

 blood 'continues its uniformity of flow through the body. 

 It is therefore evident that these organic changes, the 

 result of the increased supply of the blood to the growing 

 parts, take place independently of any increase in the 

 energy of the action of the heart. 



But why multiply causes unnecessarily ? Nature is 

 simple, and does nothing in vain. It is admitted that in 



9* 



